1721 DEVELOPMENTAL PATTERN OF DIAPHRAGM STRENGTH IN INFANCY

Abstract

Diaphragm strength was measured as maximal transdiaphragmatic pressure (Pdi) during airway occlusion in 33 infants aged 11.3 ± 0.6 (SE) months post-conception (mpc), range 8-21 mpc. All infants were asymptomatic at the time of study and required no ventilatory support. 9 infants had previous surgical correction of abdominal wall defects (gastroschisis/omphalocele), 9 infants had previous surgical correction of congenital diaphragmatic hernia, and 15 infants had no thoracic or abdominal surgery. The mean maximal Pdi for all infants was 69.7 ± 3.5 cm H2O. There were no significant differences between the 3 groups (P = 0.20). In the entire group, there was a significant correlation between maximal Pdi and age {Pdi (cm H20) = Age (mpc) x 3.4 + 30.9; r = 0.598; P = 0.0005}. In contrast, maximal Pdi in 3 ventilator dependent infants was less than 30 cm H2O. Subsequently, Pdi increased to above 40 cm H2O in these 3 infants following the ability to wean from mechanical ventilatory assistance. We conclude that diaphragm strength increases during the first year of life. Since respiratory failure may be viewed as inadequate ventilatory muscle power to overcome increased work of breathing, young infants may be at increased risk for respiratory failure relative to older infants due to decreased diaphragm strength.